ExtremePredator: Revealing ecological roles of apex predators in extreme environments

Terrestrial apex predators are well-known for important ecological roles they perform in ecosystems across the world. However, for most species we still know little about their ecological importance beyond the direct interactions with prey. This includes essential ecosystem processes such as energy flow in the food webs and nutrient transfer within and between ecosystems, as well as provision of nutrients to scavenging communities. Although poorly understood, their ecological role could be especially pronounced in less productive environments. Thus, research in extreme ecosystems represents a fertile ground to improve our understanding of the function of apex predators in ecosystem processes. To advance the science of these understudied aspects of predator ecology, we propose an innovative project with the central goal of improving our understanding of the ecological role of apex predators in nutrient cycling in extreme environments. We will achieve this by studying two key aspects of nutrient transfer: provision of nutrients to scavengers and transfer of nutrients between the ecosystems. Project will focus on two contrasting extreme ecosystems: 1) an alpine ecosystem with deep and long-lasting snow cover, and 2) a desert ecosystem with high temperatures and extremely low precipitation. In the first part, we will use camera traps to monitor the consumption of prey remains provided by apex predators (Eurasian lynx and cheetahs) in the alpine and desert ecosystems to evaluate their role as providers of nutrients to scavenger guilds. Results will be compared with ecosystems in milder environment to gain novel insights into the importance of apex predators for obligate and facultative scavengers in ecosystems with seasonally or constantly limited nutrient resources. Special focus will be on the threatened avian scavengers (golden eagles and several species of vultures), which will be equipped with GPS tags and tracked simultaneously with predators in the same area. This will provide us with unprecedented insights into the role of apex predators for conservation of endangered scavengers at the individual level. In the second part, we will assess the role of apex predators in the transfer of an essential limiting macronutrient (nitrogen) from marine to terrestrial ecosystem. We will focus on brown hyenas that regularly feed on marine mammals (seals) and study the effects of their nutrient transfer through defecation and moving of carcass to a desert environment, where already small changes in nutrient cycling could lead to strong changes in structure and functioning of the ecosystem. We will use stable isotope analysis to measure the impact of nitrogen transfer on the desert soil and vegetation, as well as track the flow of marine nitrogen into higher trophic levels, i.e. primary consumers (herbivore insects) and secondary consumers (lizards). Besides, we will measure the impact of hyena-transferred nutrients on the vitality of primary producers (woody plants and perennial grasses) and their biomass. Using such trans-disciplinary approach, we expect to discover a completely new ecological role that apex predators perform in desert ecosystems with several potential implications and opportunities for future research. Finally, we will use new insights generated through this project from extreme environments and combine them with the previous knowledge, mostly limited to more productive ecosystems, to provide a synthesis of the keystone roles of apex predators in nutrient cycling across the globe. This will allow us to present a perspective for the future of this scientific topic and identify the most pressing knowledge gaps. We believe that this may open new horizons in the research of predator ecology and stimulate further research of these underappreciated aspects and understudied environments.